Continuous heat treating furnace



'Patented Aug. l, 1939 UNITED STATES PATENT oFElcE CONTINUOUS HEATTBEATING FUBNACE Application November 17, 1937, Serial No. 175,122

5 Claims.

This invention relates to continuous furnaces and, more particularly, toan improved type of over-fired furnace for heat treating articles, suchas wire or rod stock, in improved protective containers.

It is customary to place relatively small articles, such as coils orbundles of wire or rod stock, in metallic heating boxes or containers-for the purpose of annealing, normalizing, or otherwise heat treating,so as to protect the surface of such articles from the intense heat inthe furnaces.

Heretofore, it was usually the practice to heat by the so called batchmethod, whereby a plurality of these containers holding the articles tobe heat treated were placed in a pit-type furnace and heated.. While thebatch method has proven successful and produces excellent results, therate of productivity of such a furnace is low.

Wire or rod stock has also been heat treated by the so called continuousmethod, which comprises drawing several strands at a time from coils orbundles through a furnace, or through molten salt, or other heattreating mediums. The continuous method can employ heat treating unitswhich give a greater rate of productivity than obtained by the batchmethod but the quality of the product is liable to be inferior due to acertain amount of unavoidable exposure to the air, and to the fact thatthe heating and cooling cycles are of shorter duration.

While each of these heat treating methods have `their advantages anddisadvantages, as has been explained, they use an excessive amount offuel and are, therefore, very inemcient.

It is an object of this invention to provide a heat treating furnace andmethod wherein the combined advantages of both the batch and continuousmethods are obtained; namely, the quality heating characteristics of thebatch method and the rate of productivity of the continuous method, andat the same time provide a furnace in which the fuel consumption is at aminimum.

lt is another object of this invention to provide an improved typeover-fired continuous furnace for heat treating articles in which thearticles move automatically therethrough and which includes means forcontrolling the movement of said articles therethrough.

lit is a further object of this invention to provide an improvedprotective heating box or container for use in continuous furnaces inwhich the articles to be heated are placed.

Various other objects and advantages will more fully appear during thecourse of the following specication and Will be more particularlypointed out in the appended claims.

In the accompanying drawing we have shown, for-the purpose ofillustration, one embodiment which our invention may assume in practice.

In the drawing:

Figure 1 is a longitudinal vertical section through the center of theimproved type overflred continuous furnace of our invention.

Figure 2 is a sectional view taken on the line II-II of Figure l;

Figure 3 is a sectional view taken on the line III-Ill of Figure l;

Figure 4 is a sectional view taken on the line lV-IV of Figure l; Y

Figure 5 is a longitudinal section through the center of the improvedtype protective heating box or container of our invention; and

Figure 6 is an end view thereof.

'The improved over-red continuous type furnace of our inventioncomprises a preheating chamber t?, a main heating chamber 3, a coolingchamber Land a hearth 5. The main heating chamber is separated from thecooling and preheating chambers by refractory bulkhead walls or bames tand. l, respectively. The outer ends of the cooling and heating chambersare closed by refractory Walls t and- 9, respectively. The end wall andbulkheads are provided with openings, the purpose of which will bedescribed later in the specication.

The hearth h is preferably inclined and provided with a pair oflongitudinally extending, spaced-apart guide means, such as shelves orledges, it having a longitudinally extending air passageway litherebetween centrally of the furnace in the main heating and preheatingchambers, and a similar air passageway l2 between the guide ledges inthe cooling chamber. The cooling chamber has an entering air-duct lli,`preferably disposed in the side wallthereof,and the preheating chamberhas a gas exit duct ld which is connected to the stack or to arecuperator, should one be employed. At one end of the furnace outsideof the preheating chamber is 1ocated a loading platform lb and at theopposite end of the furnace outside of the cooling chamber there isprovided an unloading platform ll and a Geneva motion-like means ltwhich is driven at a predetermined rate of speed by a source of power(not shown). v

There is provided adjacent the bulkhead 6 between the cooling chamberand the main heating chamber, a burner or burners I8 for heating themain heating chamber and furnace. Any suitable fuel, such as oil, gas,pulverized fuel or a combination thereof, can be used for heating thefurnace. If desired, the burners may be placed in the side walls of theheating chamber, although the end location, as shown, is preferred.

The improved type of protective heating boxes or containers used inconnection with this continuous furnace, in which articles such as coilsof wire and rod stock are placed for heat treating, comprise an innercylindrical body I9 having an outer diameter slightly less than theinside diameter of the coils of wire placed therein, and a substantiallylarger outer cylindrical body spaced from and enclosing the innercylindrical body. These two cylinders are securely connected together atone end by means of a flanged disklike portion 2I. On the opposite endof the cylinders there is provided a removable similar disklike endportion 22 which is adapted to be held in place on the end of thecylinders by means of the tapered key 23 which passes diametricallythrough the end of the inner cylinder in engagement therewith. The coilsof wire, rod stock or other articles to be heat treated are placed inthe container in the space between the walls of the two cylinders. Theouter surface of the inner cylinder is preferably provided with ribs orprojections 24 to prevent direct contact of the articles or coils ofwire with the hot surface of the container.

After the protective containers have been properly filled with thearticles to be heat treated they are placed on the loading platform I5at the end of the furnace and adapted to be progressively moved into thefurnace and passedsuccessively through the preheating chamber, the mainheating chamber and the cooling chamber and the openings in thebulkheads therebetween by means of gravity at apredetermined speed,which is controlled by the Geneva motion-like member I6 which alsotransfers them to the unloading platform I1 after they have been .heattreated in the furnace. It is important that the openings in thebulkheads and end walls are just large enough to allow the protectivecontainers to pass therethrough so that the gases will be directedthereby and travel properly through the' furnace. It will be understoodthat the anged portions of the disks 2I and 22 provide rolling surfacesfor the containers which are adapted to cooperate with the ledges I0 inthe hearth to rotatably guide the containers through the furnace. Itwill also be noted that these flanged portions are adapted to space thecylindrical portions of the containers from each other in order that thehot gases or cooling air may circulate around and between the containersin the furnace. When heating the work for bright annealing, the boxesmay be packed with some suitable material, such as charcoal or ironfilings, to absorb oxygen and other active harmful elements.

The path of the combustion air andgases will now be described. Theinductive effect of the burner or burners I3 firing through the burnerports 24 in the bulkheads 6 creates a partial Vacuum in the coolingchamber 4, thereby drawing cool air into thechamber through the duct I3,which is connected to the air passageway I2 in the bottom thereof.` Thisair passes, as shown by the broken arrowhead lines, into the passagewayI2, up through and around the protective containers or hot-boxes inthecooling chamber, absorbing a considerable amount of heat therefrom. Theboxes are thereby cooled and the heat removed is reclaimed by thesecondary vcombustion air. Combustion takes place as described in theheating chamber 3 above the charging line, and the combustion gases areforced downwardly by the bulkhead .1 between and around the protectvecontainers into the hearth flue or passageway II at the bottom of themain heating chamber, from which the gases pass into the preheatingchamber 2 upwardly between and around the protective containers and outthrough the exit gas flue I4 under the influence of the stack draft. Itwill be understood that the protective heating boxes or containers aresubject to a rolling motion through the furnace, thereby expediting thetransfer of heat and insuring uniformity of heating. If desired,protective boxes or containers of other forms could be used. and pushedor slid down suitable skid-rails on a hearth by some suitable mechanicalmeans, but it is preferable to use a heating box of the cylindricaltype, such as shown.

While we have in this application specically described one embodiment ofour invention, it will be understood that this embodiment is merely forthe purpose of illustration and description and that various other formsmay be devised within the scope of our invention, as dened in theappended claims.

We claim:

1. In a continuous furnace for heat treating wire and rod stock, aninclined hearth, said Yhearth having spaced-apart ledges thereinextending longitudinally of said furnace, a series of metallicprotective heating containers which are adapted to move rotatably oversaid hearth and through said furnace by means of gravity, each of saidcontainers comprising an inner cylinder having a larger outer cylinder-spaced therefrom, and having' a flanged disk-like end portion rigidlysecured to eachend thereof, a removable portion carried by at least-oneof said disks to give access to the space between the cylinders, saidspace between the cylinders adapted to receive the coils of wire or Iddstock to be treated, the anges of said disks adapted to cooperate withthe ledges in said hearth to guide said containers through the furnace,and means associated with said furnace for controlling the gravitationalmovement of said containers therethrough. f

2. In a continuous furnace for heat treating articles, a coolingchamber, .a main heating chamber and a preheating chamber, means forprogressively moving articles to be heated into and through said furnaceandv chambers, means for drawing cool air into the furnace up throughthe articles in said coolingchamber into said heating chamber, meansbetween said main heating chamber and said preheating chamber adapted todirect said air current andv gases down through the articles in saidmain heating cham-l ber into said preheating chamberand means adapted todirect said air current and gases up through the articles in saidpreheating chamber and out of the furnace.

3. In a continuous furnace for heat treating articles, an inclinedhearth, a cooling chamber, a main heating chamber, and a preheatingchamber, means for spacing the articles from each other as theyprogressively move by gravity over the hearth and through the chambersof the furnace, means for heating said furnace and drawing a cool aircurrent into the furnace up through and around said articles in saidcooling chamber into said main heating chamber, means between saidheating chamber and said preheating chamber for directing said aircurrent and gases down through said articles in said main heatingchamber into said preheating chamber, and means for directing the aircurrent and gases up through and around the articles in the preheatingchamber and out of the furnace.

d. In a continuous furnace for heat treating articles, a coolingchamber, a main heating and a preheating chamber, means forprogressively moving articles to be heated through the furnace and saidchambers, a bulkhead wall positioned between the cooling and mainheating chambers, a second bulkhead wall positioned between the main andpreheatng chambers, each of said Walls having aligned openings' thereinof dimensions slightly larger than the articles to be heated throughwhich the articles are adapted to pass,

means for firing said furnace positioned opposite a port in the upperportion of said rst named bulkhead and directed into said main heatingchamber whereby said ring means draws an air current into the furnace upthrough yand around the articles in the cooling chamber into said mainheating chamber, thence down through and around the articles in saidmain heating chamber into the preheating chamber and, finally up throughand around the articles in the preheating chamber and out of thefurnace.

5. In a continuous furnace for heat treating articles, a coolingchamber, a main heating chamber and a preheating chamber, means forprogressively moving the articles to be heated through said furnace andsaid chambers, a longitudinally extending air passageway positioned inthe hearth below the travel of the articles in saidv cooling chamber, asimilar longitudinally extending air passageway positioned in the hearthbelow the travel of the articles in said heating and preheating chambersand extending continuously therebetween the combined length thereof,means positioned between the cooling and main heating chambers fordrawing a cool air current into the furnace through an air passageway inthe cooling chamber and up through and around the articles positionedtherein, into said main heating chamber, means positioned between themain heating and preheating chambers for directing said air current downthrough and around the articles in the main heating chamber into saidair passageway located therein and into the preheating chamber, andmeans for directing said air current up through and around the articlesin the preheating chamber and out of the furnace.

GUY O. ACKERMAN, JR. PETER STEWART.

